Chronic back problems are one of the most common causes of pain and disability in the United States and other developed countries, and they account for enormous economic costs. According to at least one estimate, spinal fusion procedures, in which two adjacent vertebrae are fused together using plates, screws and other implants, are the most commonly performed surgical procedures in the United States. Spinal fusion is often performed in an attempt to increase space between the two adjacent vertebrae being operated on (“spinal distraction”) and to thus prevent impingement of the spinal cord or nerve roots branching from the spinal cord and passing through openings in the vertebral column. Unfortunately, most techniques and devices used for performing spinal fusion are relatively invasive and involve a number of risks and difficult recovery and rehabilitation.
One of the reasons that spinal fusion surgery is often very invasive is that, due to the position of the spinal cord in back of (posterior to) the central vertebral bodies of spine, many of the procedures require entering the patient through the front of the body (an “anterior approach”) and dissecting through various tissues to gain access to the spine. Fusion procedures are often performed on the cervical spine (neck region), which requires dissecting through the neck, or the lumbar spine (lower back region), which requires dissecting through the abdomen. In either case, cutting through the anterior tissues of the patient to reach the spine is not without risk. Fusion procedures may also involve relatively large plates and screws, which require a relatively large surgical access field and thus more dissection of tissue than would be ideal. Not only are these invasive spinal fusion techniques potentially risky, but they are also expensive and typically require lengthy recovery and rehabilitation times.
Therefore, a need exists for alternative devices and methods for treating spinal stenosis, particularly via fusion of adjacent vertebrae. Ideally, such devices and methods would be minimally invasive or less invasive than many of the currently available techniques. For example, it may be advantageous to have devices and methods that use a posterior approach for accessing the spine. It may also be advantageous to use smaller implants that still achieve a complete fusion. At least some of these objectives will be met by the embodiments described below.